To date, it remains undetermined what role host immunologic responsiveness bears in the clinical course of transitional cell carcinoma. We have employed in vitro parameters of cell mediated immunity in an attempt to correlate clinical course with alteration in in vitro lymphocyte responsiveness. We have employed the following in vitro studies: 1) Mixed Lymphocyte Culture (MLC), examining the ability of the patients' lymphocytes to both "stimulate" and "respond", and 2) Lymphocyte Blastogenesis induced by Concanavallin A (Con-A) and Phytohemagglutinin (PHA). We have stratified patients with bladder carcinoma in the following manner: 1) Grade and Stage of disease, 2) Therapeutic modality and its proximity in time to patient testing, and 3) the disease free interval. We have further determined that in our longitudinal studies that the parameters of most potential interest have been lymphocyte responsiveness in MLC and Con-A. This knowledge gained in the preceding two years is expected to allow us to continue our longitudinal studies with an anticipation of determining the predictive value of these in vitro parameters as now defined in patients who are subjected to extirpative surgery, radiation therapy and chemotherapy as well as evaluating those patients who are considered to be "disease free." The recognition of patterns of in vitro responsiveness which are clinically predictive should aid in the direction of patient evaluation and management.